New to pools and pool not holding chlorine

[roundhay]

We have recently moved house and now have a pool.

I walked into a local pool store saw the prices of the chemicals and being a chemist turned right around and walked back out again to look for a more sensible alternative. This brought me to TFP!

I still have lot of reading to do and I am waiting for my TF-100 kit to arrive (hopefully Tuesday) but I have started to try and get the pool sorted.

Initially the CYA was 0 but over the last week I have been adding stabilizer and have got it to 34ppm

I have also tried to shock a few times with liquid bleach 8.25% but as I can't tell how high the FC level is getting I'm not sure it I am putting enough in.

One of the questions I have is do I need to worry about how much liquid 8.25% bleach I add? I have a 23,200 gallon, vinyl lined pool.

On Monday last week I added 8 gallons of liquid bleach and had the water tested at a local pool shop the next day and the results were:

FC 0.3
CC 1.9
TA 100
pH 7.4
CYA 23

On Friday I had another go at shocking and added 11 gallons of 8.25% liquid bleach over the course of 4 hours. I took a sample to the pool store again yesterday and the results were

FC 0.6
CC 1.9
TA 86
pH 7.1
CYA 34

The stores also tested for nitrates and told me the level in my pool was very very high 140ppm. I have read up on this a bit and it does seem to be unusually high.

Questions:
1. Is there a limit to the amount of liquid bleach I can add to the pool when I shock before I risk damaging the pool?
2. Is there a test kit I can buy to check for nitrates? (Not that I don't believe the pool shop but I would like to be able to test myself)
3. If I need to get my nitrates down is the only way to drain water out of the pool?

Any help and guidance would be greatly appreciated!

 

[Butterfly]

Welcome to TFP

I walked into a local pool store saw the prices of the chemicals and being a chemist turned right around and walked back out again to look for a more sensible alternative. This brought me to TFP!

and, you have the TF100 on the way!

You can just forget about nitrates (and phospates) as they are a non-issue in a properly balanced pool, as your pool soon will be.

Since you have the CYA about 30, the normal SLAM FC is 12 ppm. I'd try to stay around that. Going way over recommended SLAM levels can bleach out the liner and do damage to equipment.

Great first post

 

[bridgman]

You can use PoolMath (button at top of page) to figure out what 12 ppm means for your pool and bleach supply. Enter pool volume at the top, then go to the bottom "Suggested Goal Levels" and set "Troublefree pools", "bleach", "vinyl". Then go back up to CYA, enter current CYA level under "Now", enter current FC level under "Now" and desired FC level (12) under "Target" -- set bleach percentage (8.25) and jug size (121 or 128 oz). If you point the cursor at the recommended amount of bleach (I got 420 oz) the field above will convert that to gallons & jugs.

If you're starting at zero, when I plugged in the numbers I got just over 3 jugs as the recommended maximum you should add at one time. If you're fighting an algae bloom the FC level can drop pretty quickly so you may end up adding a lot more than 3 jugs in a day, but recommended practice is to test & top up frequently rather than adding all the bleach at once and going to a potentially dangerous/damaging level. Sounds like you're already on top of that though.

It's probably fair to say that on average pool store testing tends to understate CYA levels, so it would be worth doing a re-test of CYA as soon as you get your kit.